Path Zipper

As the Path Zipper tool has several keypresses which can add or change its functionality, we suggest installing the free Astute Graphics plugin Astute Buddy, which creates a panel that dynamically updates to inform you of the various keys which can be pressed in the tool’s current context.

When a path contains two anchor points that are each coincident (at the same coordinates) with two points on a second path, then the section between those points may be zipped with the Path Zipper tool by placing the tool over both edges of the potential zipper and clicking. The paths do not need to be selected, but must be unlocked.

The tool previews a potential zipper using blue and red lines. The blue lines (which are dashed) indicate the original edges of the zipper, and the solid red line shows the position that the zipped paths will assume after clicking. A section of path that is already zipped will be indicated with a green line. 

Path Zipper Tool Basic Operation

By default, the new zipper is created by averaging the positions of the original edges along the length of the zipper. To make the zipper lie along one or the other of the paths’ original edges, hold down Shift or Option/Alt:

Path Zipper Tool Modifier Keys

Shift causes the zipper to run along the path which is on top in the stacking order, and vice versa. 

Because paths which you might want to zip together do not always conveniently contain coincident points at each end of the zipper, Path Zipper provides additional functions for creating such points.

First, if the paths have anchor points that are close to each other but not coincident, Path Zipper can make them coincident. When the points are within the cursor circle, they will be highlighted with semi-transparent blue dots. The new, common position of the points is shown with a red dot. After clicking, the points will be shown with a green dot, which indicates that they have been made coincident. 

Path Zipper Making Points Coincident

As with the zipping operation, a click without modifier keys simply averages the positions of the points together, while holding down Shift or Option/Alt moves the new position to one or the other of the points. If more than two points are being made coincident, another method of specifying the new point position is available: with the mouse button held down, press the A key to cycle through the different points.

Second, if only one of the paths has an existing anchor point at the desired zipper end position, then, as long as that point and at least part of the other path are within the cursor circle, a new point can be simultaneously created on the other path and made coincident. In this case, the existing point is indicated with a solid purple dot, the (virtual) new point on the other path by a hollow purple dot, and the new, common position of the points with a red dot.

Path Zipper Adding and Making Points Coincident

Again, as with the zipping operation, a click without modifier keys simply averages the positions of the points together, while holding down Shift or Option/Alt moves the new position to one or the other of the points.

Finally, the paths may intersect each other at one end of a desired zipper segment, but without an anchor point there on either path. In this case, with only the spot of intersection inside the cursor circle (indicated by a solid magenta dot), clicking will create a coincident point on each path at that spot.

Path Zipper Adding Intersection Points

There may be occasions when the points you want to make coincident (or add and make coincident, or add at an intersection) are within a potential zipper, which takes precedence. In this situation, to override zipper mode and allow for these additional functions, hold down Shift+Option/Alt. Note that with these modifier keys down, the new coincident point position will always be at the averaged position of the points. If this would result in undesired geometry, then the point(s) can always be added and/or moved manually using a different tool, such as the PathScribe tool. 

It is sometimes necessary to split a path at one of its anchor points, or remove one or more segments from a path. Although these operations can obviously be done using other existing tools, Path Zipper provides “one-click” convenience functions with which to do them, avoiding the need to change tools.

First, if a single anchor point is within the cursor circle, Option/Alt-clicking will split the path at that point (creating two paths, if the path was open). Second, if one (or more than one, as long as they are contiguous) segments of a single path are within the cursor circle, Option/Alt-clicking will remove those segments from the path (also creating two paths, if the path was open).

Path Zipper Splitting and Deleting Segments

In both cases, the Path Zipper cursor changes to indicate the function (showing scissors for split path and an “×” for delete segment), and the affected anchor point or segment(s) are highlighted in semi-transparent magenta. 

These convenience functions can speed up the process of creating centerlines from outlined paths:

Path Zipper Creating Centerline

After zipping together the two paths to create the centerline, Path Zipper, by default, automatically removes one of the two paths, since they are now duplicates. This behavior can be specified in the Path Zipper Preferences dialog (see below).